carbon reinforced neck: trussrod yes or no

[Michiel Wildenberg]

Hi,

I'm in doubt here. I want to build some guitars with a few laminated carbonfibre/epoxy sheets between my wood layers. I wonder if it still needs a trussrod. The wood will be thermo modified frake (limba/korina) with maybe a center strip of wenge or maple. They will be comercial builds so I also wonder if the lack of a trussrod will be a turn off for potential buyers.

Curious about your input.

[Jarno Verhoeven]

When in doubt, add a trussrod.

Hard to predict how/if the neck is going to move, and you will need some relief so I would add a two way trussrod.
Not sure what you are building, but on my shortscale bass builds, I got too little relief in the neck just from tension of the strings, and trussrods then allow for some tuning.
If you are building a guitar, you never know if someone decides to set the action real high and fit a set of 014 strings

[Barry Daniels]

No truss rod would definitely be a negative impact on marketability. Also, be aware that if the edges of the carbon fiber layers are exposed on the outside surface of the neck, you will have difficulty in getting a smooth surface because the carbon fiber is so much harder than the adjacent wood layers. It’s kind of like laminating wood and steel together. Just impossible to keep the surfaces even.

[Michiel Wildenberg]

Hi Barry and Jarno,

Thank you for the replies. I do wonder if a trussrod will be doing anything against the stiffness of the carbon rod, hence the carbon fibre being being up to 10 times stiffer compared to steel.

I will keep your tip in mind barry, about sanding the surface of carbon together with wood. Thanks again.

[Jarno Verhoeven]

That'll depend on the stiffness of the neck, it should move a little under string tension.
So ideally, the trussrod is only working against the string tension, not against the carbon rods/sheets. It simply has less stress being exerted on it, because of the carbon.
But if you build a neck which is way to stiff, then yes.
The travelbass I recently did has a neck which is a bit too stiff, so only after a few weeks under tension does it get a little bit of relief (but that does not have carbon rods). When adding carbon, it will not creep.

But, I glued up a neck blank last night, out of meranti, very light, probably a bit flimsy. The idea is to put carbon tubes in that (as well as a trussrod), ordered from a kite building website, keen on finding out if that works

[Michiel Wildenberg]

Hi Jarno, sounds cool. let us know how it works out. Curious about meranti as an neckwood too. I have some Meranti lying around in my workshop.

[Jarno Verhoeven]

Just found out that Ken Parker put out another video this morning. (And he does not use trussrods in his 45kUSD guitars, so, yeah)

Very interesting series, with real insights into his wild construction methods, as an engineer, it's just so fascinating to see someone this thorough.

https://youtu.be/7veBhGWi3hU?si=i5sRaNmr76SichZP